The guys and gals who attend Hogwart's School of Wizardry have to find ways to blow off steam in-between lessons and their constant battle against the dark side of the magical arts.
Some like to get stinking drunk on Firewhisky, others train tirelessly for Quidditch tournaments and magical duels, but the most popular pastime of all is the Yo Momma joke battle.
A finely crafted zinger aimed at an opponent's unwitting mother can be more damaging than a spell, and leave a nastier mark than the one old Voldy left on Harry's head.
It's fine for the students at Hogwart's to pass the time bagging on each other via Yo Momma jokes, but leave Harry and Neville out of it because talkin' smack about their mommas is just plain mean!
-Via Nerd Approved
(This is kind of hard.)